Abstract

Background

Mutations in the KRAS gene are associated with poor response to epidermal growth factor receptor inhibitors
used in the treatment of metastatic colorectal cancer. Factors influencing KRAS test results in tumor specimens include: tumor heterogeneity, sample handling, slide
preparation, techniques for tumor enrichment, DNA preparation, assay design and sensitivity.
We evaluated comparability and consistency of KRAS test results among five laboratories currently being used to determine KRAS mutation status of metastatic colorectal cancer specimens in a large, multi-center
observational study.

Findings

Twenty formalin-fixed paraffin-embedded human colorectal cancer samples from colon
resections previously tested for KRAS mutations were selected based on mutation status (6 wild type, 8 codon 12 mutations,
and 6 codon 13 mutations). We found good agreement across laboratories despite differences
in mutation detection methods. Eighteen of twenty samples (90%) were concordant across
all five labs. Discordant results are likely not due to laboratory error, but instead
to tumor heterogeneity, contamination of the tumor sample with normal tissue, or analytic
factors affecting assay sensitivity.

Conclusions

Our results indicate commercial and academic laboratories provide reliable results
for the common KRAS gene mutations at codons 12 and 13 when an adequate percentage of tumor cells is
present in the sample.